I'm trying to make a good model for a following problem.

Application is about to help, let's say, ROOMMATES to keep track of
payed/not payed BILLS for a house they live in.

I thought i could make 3 tables:

BILLS( #bill(PK),amount,date,payedBy )

ROOMMATES( #mate(PK),name )

RoomMatePayed( #bill(FK),#mate(FK))

I want to SELECT all the bills in the BILLS table and a name of roommate
fthat payed that bill.

Is it good idea to put NULL in payedBy atribut for bills that are not
payed?


Hope It's not confusing...

Thanks

luigi7up wrote:
Yes. Sounds okay to me. But what do you intend to do with the
RoomMatePayed relation?

Regards,

Michael.
--
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paid anything, don't add a row. See the beauty?

FreeData wrote:
[...]
IMO, It depends on the process. A reasonable approach would be that a
bill is added each month, and when it is payed, the bill is marked as
such.


/Lennart

Sorry , I just noticed that ROOMMATES and BILLS is not M:M relationship

so roommatePayed is not necessary as Associative entity.

My solution is going to look as follows:

BILLS(#bill (PK) ,amount,date,payedBy (FK) ) // I'm about to
put payedBy = NULL if the bill hasn't been payed yet. This is OK?

ROOMMATES(#roommate(PK),name)

This way I'll be able to create following SELECTS:
- All BILLS
- all not payed bills (where payedBy = NULL)
- all payed bills
- bills payed by some user
etc.

Hope this is 3NF now

regards ,

Luka

Michael Zedeler wrote:

luigi7up wrote:
Sounds ok to me.

Regards,

Michael.
--
Which is more dangerous? TV guided missiles or TV guided families?
I am less likely to answer usenet postings by anonymous authors.
Visit my home page at http://michael.zedeler.dk/